The present invention relates to apparatus and methods for heat removal and, more particularly, apparatus and methods for spray cooling a wedge of a generator rotor.
Heat removal in conduction cooling depends on the thickness of the conductive media. If the thickness of the conductive material can be reduced, heat removal is improved.
In generators, electromagnetic losses occur in the magnetic iron and the copper. These losses result in production of heat which must be removed to maintain overall temperature below that allowable for the copper coating and the insulation used in the construction of the generators. The rotor core, which is made of magnetic iron, can be conduction cooled by flowing fluid through the rotor shaft. However, the removal of heat from copper is better managed if oil is passed through the hollow wedges. Due to lower thermal resistance, the flow of fluid in the vicinity of copper is much more effective in removing heat from the copper and in keeping the overall temperature below the allowable limit. This is done with conduction mode of heat removal.
Since the heat transfer coefficient (HTC) depends upon the velocity of the fluid, the removal of heat is not very efficient and a very high flow is needed to create a reasonable HTC for conduction cooling. Further, because the rotor is a rotating component, having a large amount of fluid at a radius away from the rotor shaft is not desirable, especially for high powered larger diameter and high speed machines.
As can be seen, there is a need for an apparatus and method for heat removal from a rotating machine, such as a generator.